A good candidate might be Donald Knuth.

He is best known for his series of books called "The Art of Computer Programming", a multi-volume behemoth which is stuffed with comprehensive details about everything from data structures to random numbers to algorithm analysis (by the way, he's known as the father of algorithm analysis) to sorting to searching to literally everything in between. He included thesis-level questions at the end of every chapter, and wrote the examples in assembly language for clarity. Assembly language. If you thought Bill Gates was a good computer scientist, he said the following about the book:

"If you think you're a really good programmer... read Knuth's Art of Computer Programming... You should definitely send me a résumé if you can read the whole thing."

He started writing it in 1962, and has completed 4 volumes so far. Volume 5 is expected to be out around 2020, which means he will have been writing the first 5 for 58 years. And he has two more planned.

Not to mention the fact that he wrote TeX, one of the most widely used typesetting languages in the world. Or the METAFONT language. Or WEB and CWEB. Or literate programming.

He also won the John von Neumann Medal, Franklin Medal, Turing Award, and a National Medal of Science. Somebody even made up an award for his work on The Art of Computer Programming, entitling Knuth as Professor Emeritus of the Art of Computer Programming.

Pretty awesome if you ask me.